1. Field of the Invention
The invention relates to pulleys and particularly to a V-belt engaging pulley. More particularly the invention relates to a fixed position, variable pitch pulley which is stronger and more reliable and which can be produced easily and less expensively than similar pulleys, and in which the disc and hub assemblies are threadedly adjustably engaged with each other and are retained in adjusted position and mounted on a shaft by a single setscrew.
2. Description of the Prior Art
Numerous pulleys of the split sheave type for use with a V-belt have been constructed to permit adjustment of the spacing between the belt engaging pulley flanges or discs to adjust the pitch diameter of the pulley and consequently its operating characteristics. There are several general types of variable pitch pulleys. One type is provided with various mechanisms whereby one of the pulley discs is moveably mounted with respect to the other disc and is adjusted automatically by centrifugal forces acting on the pulley components. Another type of adjustable pulley has a moveable disc which is spring biased with respect to a fixed disc whereby the pitch is varied automatically in relationship to various forces acting upon the pulley. Another type is referred to as a fixed position, variable pitch pulley, which type is the subject of my invention. In this pulley type the discs are manually adjusted to a predetermined pitch and then locked or clamped in the selected position by various mechanisms.
Many of the prior fixed position, adjustable pulley constructions require large diameter bar stock from which the hubs were formed in order to provide sufficient strength and rigidity for the pulley discs. This large bar stock requires considerable machining and metal removal to form the threaded areas of the hubs to obtain the adjustment feature.
Also, most known fixed position, adjustable pulleys use two or more setscrews, at least one for adjusting the spacing between the pulley discs and another for securing the pulley on a shaft. Each setscrew requires costly drilling, tapping and reaming operations to be performed on the pulley components, and in many pulley constructions the setscrew will extend through a threaded area of another pulley component requiring deburring of the disturbed threads. In these multiple setscrew arrangements the setscrews are usually located on opposite sides of the pulley groove making it impossible for the pulley pitch to be adjusted in certain applications where the back of the pulley is inaccessable.
Other known fixed position, adjustable pulleys use wedging or clamping elements which are engaged by clamping screws such as shown in U.S. Pat. Nos. 3,132,529, 3,815,432 and 3,979,963. Other examples of related type fixed position pulley constructions are shown in U.S. Pat. Nos. 3,611,821 3,661,023 and 3,680,404.
No known fixed position, adjustable pulley construction of which I am aware has eliminated these problems by a relatively simple and inexpensive construction as set forth below and as defined in the claims.